The present invention relates to a grid, and more particularly to a grid system which imparts ions to air flowing through a duct which includes an intermediate support member constructed of non-conductive material so as to permit a uniform distribution of ions throughout the duct.
In most confined areas where large machines are in operation, such as textile mills, the air within the area has either a positive or negative electrical field. In the textile industry this field oftentimes has an adverse affect on the processing of fibers due to the buildup of either positive or negative ions within the fiber processing area. By adjusting the ion level within the area, either positive or negative or maintaining it neutral, the running conditions for the machinery within the area can be improved considerably. It has been found that the preferred ion level varies from plant to plant.
One attempt to correct this problem is disclosed in U.S. Pat. No. 3,942,072. In this particular patent two sets of grids, which are spaced sequentially from each other in a duct are utilized for imparting both negative and positive ions to the air flowing therethrough. A sensor is positioned within the room so as to measure the ion level therein. The sensor sends a signal to the control unit where the ion level is recorded. If the ion level deviates from a predetermined level the control unit, in turn, causes either a positive or negative voltage to be applied to the particular grid for either adding positive or negative ions to the air depending on the desired predetermined condition.
The grid shown in U.S. Pat. No. 3,942,072 includes grid wires which are strung between a pair of supporting members. The upper supporting member to which a voltage is imparted is normally conductive whereas the lower supporting member is non-conductive. These supporting members are insulated from the duct through which the air flows. One problem with the device illustrated in FIG. 2, of U.S. Pat. No. 3,942,072 is that flexing of the duct often will cause the grid wires to break. In an attempt to solve this problem, the grid was made in the form of a rigid rectangular frame with the grid wires strung between the upper portion of the frame to the bottom portion. Intermediate braces were also provided in this frame so as to prevent the grid wires from being blown into the adjacent grid and shorting out if they happened to break. By providing an intermediate support member, this limited the length of the broken free-swinging grid wire.
One problem encountered by providing intermediate support angle members of conductive material is that the conductive intermediate brace inhibited the emissions of ions from the grid wires closely adjacent thereto. This, in turn, reduced the efficiency of the grid as well as produced a non-uniform distribution of ions throughout the duct.